Analysts say this is because of the increased use of private security guards on ships and better co-ordination between naval patrols in the area.

After being in piracy for eight years, I have decided to renounce and quit”Mohamed Abdi HassanPirate leader known as "Afweyneh"Adado's administration chief said other top pirates had also agreed to disarm.

"We persuaded them to disarm and hand over whatever they have - boats and weapons," Mohamed Adan, the leader of the Adado administration, told the BBC Somali service.

"They realised that they cannot function as before with impunity and profits are no longer good," he said.

It was also revealed that a former president had given him diplomatic status and a diplomatic passport as an inducement to give up his pirate network.

Multi-million dollar ransoms"After being in piracy for eight years, I have decided to renounce and quit, and from today on I will not be involved in this gang activity," AFP news agency quotes Afweyneh as saying at a news conference in Adado on Wednesday.

"I have also been encouraging many of my colleagues to renounce piracy too, and they have done it," he said.

According to AFP, his pirates were reportedly involved in the 2009 capture of Ukrainian ship MV Faina, which was carrying Russian-made tanks and weapons. It was freed after a ransom of $3.2m (£2m) was paid following months of painstaking negotiations.

The 2008 capture of the Saudi-owned Sirius Star supertanker is also believed to be attributable to his men, the agency says.

The tanker, loaded with two million barrels of oil, was released after two months in return for a ransom believed to have been $3m, which was parachuted on to the deck of the ship by helicopter.

The British couple Paul and Rachel Chandler were also held in Adado for more than a year after they were seized from their yacht off the Seychelles in 2009.

Mr Adan said Somali elders in Hobyo and Harardhere - notorious pirate strongholds along the coast - had also helped with the negotiations to persuade the pirates to stop their activities.